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  • C08G61/126—Macromolecular compounds containing atoms other than carbon in the main chain of the macromolecule derived from five- or six-membered heterocyclic compounds, other than imides derived from five-membered heterocyclic compounds with a five-membered ring containing one sulfur atom in the ring
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  • H10K85/111—Organic polymers or oligomers comprising aromatic, heteroaromatic, or aryl chains, e.g. polyaniline, polyphenylene or polyphenylene vinylene
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  • H10K85/113—Heteroaromatic compounds comprising sulfur or selene, e.g. polythiophene
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  • H10K85/111—Organic polymers or oligomers comprising aromatic, heteroaromatic, or aryl chains, e.g. polyaniline, polyphenylene or polyphenylene vinylene
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  • H10K85/324—Metal complexes comprising a group IIIA element, e.g. Tris (8-hydroxyquinoline) gallium [Gaq3] comprising aluminium, e.g. Alq3
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  • Y02E10/549—Organic PV cells

Definitions

• organic semiconductors In a series of different types of applications which can be classed within the electronics industry in the widest sense, the use of organic semiconductors as functional materials has been reality for some time or is expected in the near future. For instance, organic charge transport materials (generally hole transporters based on triarylamines) have already found use for several years in copying machines.
• organic transistors O-TFTs, O-FETs
• O-ICs organic integrated circuits
• O-SCs organic solar cells
• OLEDs Organic electroluminescent devices
• LCDs liquid-crystal displays
• EP 0895442 describes OLEDs in which not more than 10 13 electron spins per mg of compound exist, since these function as traps for electrons and holes. These electron spins are suspected to stem, inter alia, from contaminations of the compounds and can be removed effectively, for example, by sublimation.
• EP 1087448 states that the presence of ionic impurities from the first and second group of the Periodic Table of the Elements, in particular Na and K, leads to high current flow without recombination and light emission in the device, which unnecessarily generates heat which damages the device. Therefore, organic semiconductors are proposed there, whose content of the abovementioned ionic impurities is less than 0.1 ppm. To purify the materials, the methods customary for organic compounds, such as recrystallization, sublimation, dialysis, etc, are listed.
• JP 2004/039566 describes how use of chelating agents can remove metallic impurities which have been used, for example, as catalysts in the synthesis from organic semiconductors.
• the use of complexing agents for this purpose is also described, for example, in WO 03/048225 and in WO 00/53656.
• JP 2004/039567 describes how use of chelating agents can remove boron impurities which may be present as by-products of the synthesis from organic semiconductors.
• this method has the disadvantage that it can remove free boron impurities but not impurities (or incompletely reacted reactants) which are bound to the semiconductor and do not react with the chelating agent. As a result, the boron content cannot be lowered to a very low level.
• JP 2003/347624 describes how use of supercritical solvents can lower the content of impurities in organic semiconductors down to between 0.01 and 50 ppm.
• this method also has the disadvantage that it can only capture free impurities, but not impurities which are bonded covalently to the reaction by-products (or incompletely reacted reactants) of the organic semiconductor, for example unreacted functional groups, for example halogen substituents or boronic acid derivatives.
• EP 1063869 describes OLEDs in which the organic components contain less than 500 ppm of impurities, in particular halogenated impurities.
• impurities in particular halogenated impurities.
• in-house experiments demonstrate that such a level of impurities is still more than one order of magnitude too high to achieve the desired effect.
• a content of halogenated impurities in the region of close to 500 ppm might perhaps achieve the first small effects, but the object of reproducibly obtaining long-lifetime organic electronic devices is not achieved in this way.
• the invention provides electronic devices comprising at least one organic semiconductor, characterized in that the content of at least one of the halogens fluorine, chlorine, bromine and/or iodine in the organic semiconductor is less than 20 ppm.
• Organic semiconductors are typically especially those in whose production a reactive bromine or else a reactive iodine or chlorine is involved in one of the following reactions in particular: Suzuki coupling, Stille coupling, Yamamoto coupling, Heck coupling, Hartwig-Buchwald coupling, Sonogashira coupling, Negishi coupling or Hiyama coupling.
• Organic semiconductors are also typically especially those in whose synthesis a reactive chlorine is involved in a Gilch reaction. This reactive halogen is eliminated during the reaction.
• the invention therefore in particular provides electronic devices which comprise at least one organic semiconductor which has been obtained by a reaction in which a reactive halogen was involved, characterized in that the content of at least one of the halogens fluorine, chlorine, bromine and/or iodine in the organic semiconductor is less than 20 ppm. In particular, the content of the halogen which was involved in the reaction to synthesize the organic semiconductor is less than 20 ppm.
• the electronic devices comprising at least one organic semiconductor are preferably selected from the group of electronic devices consisting of organic and polymeric light-emitting diodes (OLEDs, PLEDs), but also organic field-effect transistors (O-FETs), organic thin-film transistors (O-TFTs), organic integrated circuits (O-ICs), organic solar cells (O-SCs), organic field-quench devices (O-FQDs), organic light-emitting transistors (O-LETs), light-emitting electrochemical cells (LECs) or else organic laser diodes (O-Laser), to name just a few applications.
• O-FETs organic field-effect transistors
• O-TFTs organic thin-film transistors
• O-ICs organic integrated circuits
• O-SCs organic solar cells
• O-FQDs organic field-quench devices
• O-LETs organic light-emitting transistors
• LECs light-emitting electrochemical cells
• O-Laser organic laser diodes
• Preferences is further given to electronic devices, characterized in that all organic semiconductors in all layers contain less than 20 ppm of bromine.
• organic semiconductors are low molecular weight, oligomeric, dendritic or polymeric, organic or organometallic compounds which, as a solid or as a layer, have semiconducting properties, i.e. in which the energy gap between conduction and valence bands is between 1.0 and 3.5 eV.
• the organic semiconductor used here is either a pure component or a mixture of two or more components, of which at least one has to have semiconducting properties. In the case of the use of mixtures, it is, however, not necessary that each of the components has semiconducting properties.
• the organic semiconductor in the electronic device is polymeric.
• polymeric organic semiconductors are in particular
• low molecular weight organic or organometallic semiconductors are used, a low molecular weight compound being understood to be a compound having a molecular weight of less than 10000 g/mol, preferably less than 5000 g/mol.
• dendritic organic or organometallic semiconductors are used.
• dendritic organic or organometallic semiconductors can be found in WO 99/21935, WO 01/059030 and WO 02/066552.
• the content of at least one halogen, or the content of bromine, or in each case the content of fluorine provided that fluorine is not a constituent part of the chemical structure, chlorine, bromine and iodine, in the organic semiconductor is preferably less than 10 ppm, more preferably less than 5 ppm, even more preferably less than 1 ppm, in particular less than 0.1 ppm. This is the case especially when this corresponding halogen was involved in a preceding reaction step in the production of the organic semiconductor. It has been found that it is possible with such a low content of halogens to achieve particularly good results in the electronic devices. This relates in particular to the heavier halogens chlorine, bromine and iodine.
• Halogens in particular bromine and iodine or else chlorine, are frequently present as an impurity in organic semiconductors when metal-catalyzed coupling reactions (for example Suzuki coupling, Yamamoto coupling, Hartwig-Buchwald coupling, etc) have been employed for the synthesis, as are widely used for the synthesis of organic semiconductors. Since these coupling reactions are also used to synthesize conjugated polymers, polymeric organic semiconductors also have these impurities. Chlorine is present as an impurity in particular after the synthesis of poly-para-phenylenevinylenes by the Gilch method, since this method starts from halomethyl-substituted, preferably chloromethyl-substituted, aromatics.
• impurities may be present either in free form, for example as an anion or as halogen bonded to a low molecular weight structure with C—X bond, or bonded covalently to the organic semiconductor or its by-products or reactants.
• covalently bonded halogens cannot be removed by simple purification processes, for example recrystallization, sublimation, reprecipitation, etc. It is thus barely possible by standard methods of the prior art to remove them to such an extent that the content of these impurities is sufficiently low to ensure good electronic properties.
• the electronic properties, in particular the lifetime, but also efficiency, of the organic electronic device can be enhanced still further when, in addition to the low content of halogens, the content of other elements, which may be present as impurities or in by-products, in the organic semiconductor is below a certain content.
• the content of sulphur in the organic semiconductor is less than 20 ppm, more preferably less than 10 ppm, even more preferably less than 5 ppm, in particular less than 1 ppm, provided that sulphur is not bonded into the organic semiconductor as a constituent part of the chemical structure, for example in thiophenes.
• Sulphur impurities can stem, for example, from the workup of the organic semiconductors when, for example, the metal is removed after a metal-catalyzed coupling reaction by extraction with thiocarbamate solution. Sulphur impurities can also stem from the synthesis when, for example, sulphonates have been used in a Suzuki coupling.
• the content of phosphorus in the organic semiconductor is less than 20 ppm, more preferably less than 10 ppm, even more preferably less than 5 ppm, in particular less than 1 ppm, provided that phosphorus is not bonded into the organic semiconductor as a constituent part of the chemical structure, for example in triarylphosphines.
• Phosphorus impurities may stem, for example, from the catalyst which is used for metal-catalyzed coupling reactions, for example from aliphatic or aromatic phosphine ligands, but also from phosphate-containing bases or buffer systems.
• the content of silicon in the organic semiconductor is less than 20 ppm, more preferably less than 10 ppm, even more preferably less than 5 ppm, in particular less than 1 ppm, provided that silicon is not bonded into the organic semiconductor as a constituent part of the chemical structure.
• Silicon impurities may stem, for example, from glass reaction vessels or tank enamellings, in which the reactions were carried out, and are leached out of the glass or enamel especially as a result of addition of fluoride and/or basic reaction conditions as are required for some coupling reactions (fluorosilicates). Silicon impurities may also stem from the synthesis when, for example, arylsilanes are used in an Hiyama coupling.
• the content of boron in the organic semiconductor is less than 20 ppm, more preferably less than 10 ppm, even more preferably less than 5 ppm, in particular less than 1 ppm, provided that boron is not bonded into the organic semiconductor as a constituent part of the chemical structure, for example in triarylboranes.
• Boron impurities may stem from the glass reaction vessel (borates) in which the reaction was carried out. However, they may also stem from the reaction itself when, for example, boronic acid derivatives are used in Suzuki coupling reactions. These may then be present either in free form as reaction by-products or bonded to the organic semiconductor as incompletely reacted reactants.
• the content of tin and/or of zinc in the organic semiconductor is less than 20 ppm, more preferably less than 10 ppm, even more preferably less than 5 ppm, in particular less than 1 ppm.
• Tin or zinc impurities may stem from the reaction when, for example, tin or zinc derivatives are used in Stille or Negishi coupling reactions. These may then be present either in free form as reaction by-products or bonded to the organic semiconductor as incompletely reacted reactants.
• the content of the abovementioned impurities may be determined by various analytical standard methods. Examples here include ICP-MS (inductively coupled plasma mass spectrometry), LA-ICP-MS (laser ablation inductively coupled plasma mass spectrometry), GDMS (glow discharge mass spectrometry), SIMS (secondary ion mass spectrometry), ICP-OES (inductively coupled plasma optical emission spectroscopy) and preferably neutron activation.
• ICP-MS inductively coupled plasma mass spectrometry
• LA-ICP-MS laser ablation inductively coupled plasma mass spectrometry
• GDMS low discharge mass spectrometry
• SIMS secondary ion mass spectrometry
• ICP-OES inductively coupled plasma optical emission spectroscopy
• the invention further provides for the use of organic semiconductors having a content of at least one of the halogens fluorine, chlorine, bromine or iodine, in particular bromine, of less than 20 ppm in an electronic device.
• organic semiconductors having a content of at least one of the halogens fluorine, chlorine, bromine or iodine, in particular bromine, of less than 20 ppm in an electronic device.
• a further aspect of the present invention are organic semiconductors obtainable by a process comprising the following steps:
• the halogen content in particular the bromine content when reactive bromine was involved in the reaction, is typically distinctly higher than 20 ppm.
• the organic semiconductor can be aftertreated in situ directly after the last synthesis stage. However, it is preferred to isolate the organic semiconductor as a solid and to carry out the aftertreatment in a separate reaction step.
• Suitable reagents for aftertreatment are those which react with organically bonded halogens, in particular with halogens bonded to aromatics.
• Suitable for this purpose are in particular simple hydrides of the alkali metals or alkaline earth metals, for example NaH, MgH 2 or LiH, ternary hydrides containing boron or aluminium, for example LiAlH 4 , NaAlH 4 , LiBH 4 , NaBH 4 , NaB(CN) 3 H, LiAlR 3 H, LiAl(OR) 3 H, NaBR 3 H or NaB(OR) 3 H where R is a C 1 to C 6 alkyl group, alanes, for example AlH 3 or R 2 AlH where R is a C 1 to C 6 alkyl group, or boranes, for example B 2 H 6 , BH 3 .THF or R 2 BH where R is a C 1 to C 6 alkyl group.
• simple hydrides of the alkali metals or alkaline earth metals for example NaH, MgH 2 or LiH
• ternary hydrides containing boron or aluminium for example Li
• transition metal hydrides which, if anything, have the character of alloys of metals with hydrogen, in particular titanium hydride, hydrides of the titanium alloys with Cr, Mn or Ni, and also hydrogen-containing alloys containing magnesium and/or aluminium, which may also comprise further metals for activation.
• complex transition metal hydrides for example cyclopentadienyl metal hydrides, e.g. (Cp) 2 TiH 2 or (Cp) 2 MoH 2 , or carbonyl metal hydrides, e.g. Mn(CO) 5 H or Fe(CO) 4 H 2 .
• main group element hydrides for example silanes, alkylsilanes or halosilanes, e.g. SiH 4 , Me 3 SiH, H 3 SiBr, etc, or stannanes, alkylstannanes or halostannanes, for example SnH 4 , Bu 3 SnH, Cl 3 SnH, etc. All of these hydrides may optionally also be used in combination with a Lewis acid, for example AlCl 3 or ZnCl 2 , to promote the reaction.
• a Lewis acid for example AlCl 3 or ZnCl 2
• homogeneous or heterogeneous transition metal catalysts especially containing elements of the platinum group, in particular rhodium, iridium, palladium or platinum, which react together with elemental hydrogen, optionally under pressure, or a hydride source.
• elements of the platinum group in particular rhodium, iridium, palladium or platinum, which react together with elemental hydrogen, optionally under pressure, or a hydride source.
• An example here is Vaskas's complex ((PPh 3 ) 2 Ir(CO)Cl) in combination with H 2 .
• hydride sources which may be used are organic compounds, for example hydroquinones, optionally in combination with a catalyst.
• organometallic reagents which enter into transmetallation and thus exchange the halogen for a metal atom, for example alkyl- or aryllithium reagents, alkyl or aryl Grignard reagents, or alkyl- or arylzinc reagents.
• the metalcontaining derivatives of the organic semiconductors which are obtained by transmetallation or reaction with reactive metals may be converted in a further step to the final compound.
• a useful reaction here is in particular the hydrolysis with a protic compound, for example with water or an alcohol, which results in the unsubstituted compound.
• a further example of a useful reaction is a metal-catalyzed coupling reaction with an aryl bromide or iodide, which forms an aryl-substituted compound (for example Negishi coupling).
• a further preferred method for aftertreating halogenated organic semiconductors is the coupling with amines, aryl, vinyl or acetylene compounds, etc. under transition metal catalysis.
• Useful examples here are the reaction with a vinyl-H compound (Heck coupling), with an arylboronic acid derivative (Suzuki coupling), with an aryl-tin derivative (Stille coupling), with an aromatic amine (Hartwig-Buchwald coupling), with an acetylene-H compound (Sonogashira coupling) or with an arylsilane derivative (Hiyama coupling), in each case catalyzed by palladium.
• aryl halides particularly bromides or iodides, with use of nickel compounds (Yamamoto coupling).
• the aftertreatment may be carried out in organic solvents. However, it may also be carried out in liquefied or supercritical gases, for example in liquid NH 3 or SO 2 , or in supercritical CO 2 . These solvents offer the advantage that, after the solvent has been evaporated off, the prepurified product can be isolated in a simple manner.
• a preferred after treatment reaction is a coupling reaction under transition metal catalysis, in particular palladium catalysis.
• a Suzuki coupling in which the reagent used is a low molecular weight boronic acid derivative. This is especially true of polymeric organic semiconductors, since a possible excess of low molecular weight boronic acid derivative in these can be removed after the reaction in a simple manner, for example by washing or reprecipitation.
• a further preferred aftertreatment reaction is the reaction with metal organyls or reactive metals to form an organometallic intermediate of the organic semiconductor and subsequent hydrolysis. This is especially true when the organic semiconductor, apart from the halogen impurities, bears no reactive groups which can react with metal organyls or reactive metals. Preference is given to the reaction with organolithium compounds at low temperatures and with magnesium to form a Grignard reagent at elevated temperature, followed by hydrolysis with water or alcohols.
• a further suitable aftertreatment step for the reduction of the boron content is deboronation, for example with various acids (e.g. H. G. Kuivila et al., J. Am. Chem. Soc. 1960, 82, 2159-2163).
• step c) It may also be viable to repeatedly carry out the same or different aftertreatment steps (step c)) successively in order to even further lower the content of halogens and any other impurities.
• the invention further provides solutions of one or more inventive organic semiconductors in one or more solvents. It is preferred when the content of the abovementioned impurities in the solvents is likewise below the abovementioned limiting values.
• inventive electronic devices comprising at least one organic semiconductor, whose content of bromine, or of halogens in general and, if appropriate, also of further impurities, as described above is below certain limiting values, have some crucial advantages:
• organic field-effect transistors O-FETs
• organic thin-film transistors O-TFTs
• organic integrated circuits O-ICs
• organic solar cells O-SCs
• organic field-quench devices O-FQDs
• organic light-emitting transistors O-LETs
• LOCs light-emitting electrochemical cells
• O-Laser organic laser diodes
• 1,6-bis(Spiro-9,9′-bifluoren-2-yl)pyrene was prepared according to standard methods by Suzuki coupling from spiro-9,9′-bifluorene-2-boronic acid and 1,6-dibromopyrene.
• 8.31 g (10 mmol) of 1,6-bis(spiro-9,9′-bifluoren-2-yl)pyrene having a purity greater than 99.9% by HPLC and a bromine content of 120 ppm (determined by neutron activation) were suspended in 100 ml of absolute THF. The pale yellow suspension was cooled to ⁇ 78° C.
• the OLEDs were produced by a general process according to WO 04/058911.
• the compound H1 (from Example 1, bromine content 8 ppm) was used in the emission layer, either as pure layer or as a host material together with a dopant. In comparison, the same compound which had not been separately aftertreated and whose bromine content was 120 ppm was also used.
• OLEDs were characterized in a standard manner; for this purpose, the electroluminescence spectra, the efficiency (measured in cd/A), the operating voltage and the lifetime were determined.
• the lifetime is defined as the time after which the initial brightness of the OLED has fallen by half at a constant current density of 10 mA/cm 2 .
• the EMLs comprise either pure 1,6-bis(spiro-9,9′-bifluoren-2-yl)pyrene (host H1) or the dopant D1 (synthesized according to DE 102004031000.9) doped into 1,6-bis(spiro-9,9′-bifluoren-2-yl)pyrene (host H1).
• the comparative examples used are OLEDs which comprise 1,6-bis(spiro-9,9′-bifluoren-2-yl)pyrene which has not been aftertreated in the emitting layer, according to the prior art.
• Polymer P1 was synthesized according to standard methods by Suzuki coupling (WO 03/048225) from 50 mol % of M1, 30 mol % of M2, 10 mol % of M3 and 10 mol % of M4 with addition of 0.8 mol % of the end-capper E1.
• the solution was cooled to 60° C. and admixed with 40 ml of a 10% sodium thiocarbamate solution. The thus obtained mixture was stirred at 60° C. for a further 3 h. The solution was cooled to room temperature, the phases were separated and the organic phase was washed three times with H 2 O.
• the polymer was isolated by precipitation from methanol and purified by reprecipitating twice from THF/methanol. The bromine content of the aftertreated polymer was 15 ppm (determined by neutron activation).
• the polymers were investigated for use in PLEDs.
• the PLEDs were each two-layer systems, i.e. substrate//ITO//PEDOT//polymer//cathode.
• PEDOT is a polythiophene derivative (Baytron P, from H. C. Stack, Goslar).
• the layer thickness of the PEDOT layer and of the polymer layer was in each case 80 nm.
• the cathode used in all cases was Ba/Ag (Aldrich). How PLEDs can be prepared is described in detail in WO 04/037887 and the literature cited therein.
• inventive polymers which have a lower bromine content are distinctly better in the electroluminescence than polymers having a higher bromine content according to the prior art, especially in the lifetime, but also in the efficiency.
• Polymer P4 was treated a further three times with end-capper E2 analogously to Example 6. After each aftertreatment, the bromine content was determined and the polymers were tested in a PLED after each aftertreatment. The results which were obtained with this polymer are compiled in Table 4. It can be seen that each aftertreatment step results in the bromine content in the polymer falling further and finally being at value of less than 0.1 ppm. In parallel, the efficiency and in particular the lifetime rise significantly.

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